1. Field of the Invention
The present invention relates to a robot controller for controlling motions of a robot.
2. Description of the Related Art
Recently, humanoid robots, particularly walking of humanoid robots, are attracting attentions of the researchers. Most of the studies relating to walking of the humanoid robots use the ZMP (Zero Moment Point) criteria. The ZMP criteria include a control to retain the ZMP within a support polygon. Specifically, this approach includes modeling the humanoid robot and the environment around the robot, and solving a differential equation. However, accurate modeling becomes difficult if there are unknowns. Furthermore, a real time control becomes difficult because time is taken in solving the differential equation.
One approach is to use a method that does not employ the ZMP criteria at all. There have been known techniques, for example, that make use of a cyclic movement of a movable section of a robot, and adjust a phase of the cyclic movement so as to stabilize posture of the robot (See Japanese Patent Laid-Open Publication No. 2005-96068). The movable section can be a leg or an arm of a robot.
However, humanoid robots can perform various motions and switch from one motion to another. For example, a humanoid robot can switch from kicking motion to walking motion. When the humanoid robot switches motions, its cyclic movement is effected and may severely deviate from a true cyclic movement and make the posture of the humanoid robot unstable.
There is a need to develop a technique enabling switching between various motions without making a humanoid robot unstable.